This application is based upon and claims benefit of priority of Japanese Patent Application No. 2000-231648 filed on Jul. 31, 2000, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a method of fixing a cylindrical member in a hole by calking. For example, an electromagnetic valve of an ABS actuator is fixed by calking in a hole formed in a housing.
2. Description of Related Art
It is generally known to fix a cylindrical member in a hole by calking. In the conventional calking, either a calking force or a calking stroke is kept constant. The former is called constant pressure calking and the latter is called constant stroke calking. In both calking processes, however, it has been difficult to attain quality calking because dimensions of members to be calked are not always constant. It is especially important to attain quality calking when a high strength and a high sealing ability of a calked portion are required.
To improve the calking quality, it could be possible to machine the members to be calked with high accuracy or to determine calking conditions according to dimensions of respective members. However, it is time-consuming and costly to employ such a process.
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide an improved calking method in which quality calking is attained in a simple manner.
A member having a cylindrical portion is fixed by calking to a depressed portion formed in a housing. A groove is formed on the outer periphery of the cylindrical portion. A peripheral portion of the depressed portion is pressed down to plastically deform a part of the housing material such as aluminum and to supply the deformed housing material into the groove. Thus, the member having the cylindrical portion is fixed to the housing. This calking method is used, e.g., for fixing electromagnetic valves to an aluminum housing of an ABS actuator.
In the process of deforming the housing material, a relatively large amount of calking force is required until the housing material begins to be supplied into the groove. On the other hand, a relatively small amount of calking force is required during the course of filling the groove with the housing material. This means that a calking curve showing the amount of calking force required relative to the calking stroke has an inflection point. In other words, an inclination of the calking curve is large up to the inflection point and becomes small after the inflection point.
During the calking process, the calking force and the calking stroke are measured to detect the inflection point based on the inclination of the calking curve. A point where the inclination becomes lower than a predetermined value is determined as the inflection point. Alternatively, a point where the inclination changes considerably may be determined as the inflection point. After the calking process reached the inflection point, the calking is performed with a predetermined constant stroke. In this manner, a substantially constant amount of the deformed housing material is supplied into the groove, if there are certain dimensional deviations in members to be calked together. The constant stroke is predetermined, so that an adequate amount of the housing material for obtaining quality calking is supplied into the groove. Instead of setting the constant stroke, a predetermined constant calking force may be added after the inflection point.
According to the present invention, the quality calking having a high mechanical strength and a high sealing ability is realized because a proper amount of the housing material is supplied into the groove.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiment described below with reference to the following drawings.